Reciprocating positive displacement pump for deionized water and method of cooling and lubricating therefor

ABSTRACT

A method of lubricating and cooling a de-ionized water positive displacement pump having a reciprocating piston using tap water instead of de-ionized water to cool and lubricate the plunger and seals, resulting in longer service life of the pump.

BACKGROUND OF THE INVENTION

The present invention is directed to a fluid reciprocating positive displacement pump for de-ionized water and in particular to a method of lubricating and cooling such a pump with tap water.

More practically, a three-piston/plunger pump is a positive displacement, reciprocating pump. With each revolution of the crankshaft there is a direct motion of the plunger rods (piston) resulting in a positive output of flow from the pump. The pistons are offset 120° in relation to each other. The output of the pump (flow) is in direct relation with the RPM of the pump. The bore and stroke determine the amount of liquid handled with each revolution.

Pumps of this type have a particular application in high pressure pumping de-ionized water for many uses including electronic part processing. The pumps typically have a high-pressure Teflon® seal distal from the motor rotating shaft within the pump housing and low-pressure seals made, for example, from butylnitrile located proximal to the motor shaft within the pump housing.

This style of pump requires lubrication and cooling to insure its longevity. Typically, the pump is cooled and lubricated between the seals by the fluid being pumped. De-ionized water from the inlet source is directed to the pump head and is circulated between the high pressure seal and the low pressure seal.

De-ionized water is usually stored and used at ambient temperatures of 90°-100° F. Hence, this cooling technique is not optimal.

It is well known that de-ionized water is not very conductive (15-16 megaohms) versus tap water which is more conductive (0-2 megaohms). This means that de-ionized water is highly abrasive of the seals in that it provides no lubrication while tap water with its ions performs lubrication.

Because the plunger is not well cooled and the seals are not lubricated, pump failure occurs. If a high pressure seal fails, low pressure seal failure soon follows signified by a leaky pump housing spraying pumped de-ionized water. The crankshaft side of the low pressure seal is exposed to atmosphere. Thus, cooling and lubricating of this seal is also very important. If the low pressure seal fails, the cooling/lubricating water leaks through the pump housing.

There is a need for a new lubrication method for pump seals which uses tap water rather than de-ionized water for lubrication.

SUMMARY OF THE INVENTION

A method of lubricating and cooling a de-ionized water positive displacement pump having reciprocating pistons/plungers using tap water instead of de-ionized water to cool and lubricate the plunger and seals, resulting in longer service life of the pump.

A principle object and advantage of the present invention is that the use of tap water instead of de-ionized water to cool and lubricate the pump's high-pressure seal, plunger and low pressure seal results in longer service life and less maintenance of the reciprocating positive displacement pump for de-ionized water.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-section of a pump with lubrication provided by tap water as opposed to de-ionized water.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A reciprocating positive displacement three-piston pump for use with the present invention is shown in FIG. 1 as reference numeral 10.

The pump 10 includes a pump housing 11 and a crankshaft housing 12 encompassing a crankshaft 14 externally driven (not shown) connecting rod 16. The crankshaft 14 is connected to a piston or plunger 18 in a manner well-known through rod 16 to produce reciprocating motion of the plunger or piston 18 as the crankshaft 14 rotates.

The plunger 18 reciprocates within a pump chamber 20 and cooling and lubricating chamber 21. The pump chamber 20 has a low-pressure seal 22 which seals the pump chamber 20 within the pump housing 11. Backup seal 23 protects the crankshaft housing 12, crankshaft 14, rod 16 and their typical petroleum lubricants. The pump chamber 20 has a high-pressure seal 24 which seals the compression chamber 26 from the cooling and lubricating chamber 21 and low-pressure seal 22.

The pump 10 has an inlet chamber 28 which receives de-ionized water A from a source (not shown). The inlet chamber is normally closed by an inlet valve 30.

The pump 10 has an outlet chamber 32 for pumping pressurized de-ionized water B to a destination (not shown). The outlet chamber 32 is normally closed by an outlet valve 34.

The plunger 18 is lubricated by tap water C flowing from a source (not shown) through an inlet 36 to contact the plunger 18, the high-pressure seal 24 and the low-pressure seal 22 and, thus, lubricate and cool the plunger 18 and seals 22 and 24. Tap water D is then discharged through an outlet 38. In the context of this application, “tap water” shall be defined as any non-de-ionized water such as city water. City water typically is 30-40 PSI. In this application, the city water is suitably valved down to 2-3 PSI.

By this arrangement and method of cooling and lubricating, pump 10 and its constitutent parts have significantly greater longevity in between service and maintenance down times. This is because tap water C at 40°-50° has greater cooling capacity than de-ionized water A at 90°-100° F. Also, tap water C is a better lubricant with its metal ions than abrasive de-ionized water A.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar to or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety to the extent allowed by applicable law and regulations. In case of conflict, the present specification, including definitions, will control.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention. 

1. A method for lubricating and cooling a reciprocating plunger positive displacement pump for de-ionized water having a crankshaft housing and a pump housing with a compression chamber and a cooling and lubricating chamber and a compressing plunger passing through the cooling and lubricating chamber into the compression chamber and having a high pressure seal between the compression chamber and the cooling and lubricating chamber and a low pressure seal between the cooling chamber and the crankshaft housing, comprising the steps of: (a) connecting the cooling and lubricating chamber to a source of tap water and a destination for flushing tap water; (b) circulating tap water through the cooling and lubricating chamber to cool and lubricate the plunger and the seals; and (c) flushing the circulating tap water to the destination.
 2. The method of claim 1, further comprising the step of valving the tap water to low pressure before circulating.
 3. A reciprocating positive displacement pump for de-ionized water, comprising: a) a crankshaft housing; b) a pump housing connected to the crankshaft housing with a de-ionized water inlet and a pressurized de-ionized water outlet; c) an inline compression chamber and a cooling and lubricating chamber; d) a reciprocating compression plunger extending from the crankshaft housing, through the cooling and lubricating chamber and into the compression chamber; e) a high pressure seal between the compression chamber and the cooling and lubricating chamber about the plunger; f) a low pressure seal between the cooling and lubricating chamber and the crankshaft housing about the plunger; g) a tap water inlet into the cooling and lubricating chamber for bringing tap water thereinto; and h) a flushing tap water outlet out of the cooling and lubricating chamber for removing the tap water out of the cooling and lubricating chamber. 